replacing speedometer on 2008 Toyota Tacoma?

[I me and myself]

I'm out of warranty on my 2008 Toyota Tacoma; and my speedometer is not working. My speedo read 42k mi the last time it worked. the display is dead/blank now. I found one on-line from an auto wrecker.The replacement unit reads 65k miles says the auto wrecker. If my brother installs the replacement unit for me, will it read 42k or 65k? I've called a few shops and they don't know. OMG! some mechanic says the mileage is stored in the ecu ..and it will read my old mileage of 42k. Others tell me it will read 65k because the memory is stored in the speedo gauge itself. A "clown" mechanic told me it will combine the two and read ..107k....hilarious? or ridiculous?!

Please someone out there who works for Toyota, give me an answer? Vehicle is base model 4 cyl and automatic transmission. Please let me know so I can decide if I will purchase from the wrecking yard..

Thanks in advance!

Megan